1. Field of the Invention
This invention relates to methods of manufacture of ceramic honeycomb structures used as particulate filters, catalytic converters, and in particular, to a method for producing a ceramic honeycomb body that includes removing material from at least one of the ends of the honeycomb body with a rotating abrasive tool, thereby providing an end surface with surface characteristics heretofore unachievable.
2. Description of the Related Art
Ceramic honeycomb structures having traverse cross-sectional cellular densities of approximately 1/10 to 100 cells or more per square centimeter have several uses, including solid particulate filter bodies and catalytic converter substrates. In certain uses, such as in particulate filters, the configuration may require selected cells of the porous ceramic honeycomb structure to be sealed or plugged, such as at one or both of the respective ends thereof. These uses generally require the production of these honeycomb structures to exacting length dimensions. The manufacture of these honeycomb structures from plasticized powder batches comprising inorganic powders dispersed in appropriate binders is well known. U.S. Pat. Nos. 3,790,654; 3,885,977; and 3,905,743 describe extrusion dies, processes, and compositions for such manufacture, while U.S. Pat. Nos. 4,992,233 and 5,011,529 describe honeycomb structures of similar cellular structure extruded from batches incorporating other powders.
As an example, reference numeral 9 (FIG. 1) generally designates a prior art, honeycomb structural body that is generally well known. The body includes a honeycomb structure 12 formed by a matrix of intersecting, relatively thin, porous walls 14 surrounded by an outer wall 15 (otherwise referred to as a skin), which, in the illustrated example, is provided in a circular cross-sectional configuration having a maximum width dimension (W). The walls 14 extend across and between a first end 13 that includes a first end face 18, and a second end 17 that includes an opposing second end face 20, and form a large number of adjoining hollow passages or cell channels 22 which also extend between and are open at the end faces 18, 20 of the filter body 10.
To form the filter 10 (FIGS. 2 and 3), some of the cells 22 are sealed, for example at one end of at least some of the cells. In one example, a first subset 24 of the cells 22 are sealed at the first end face 18, and a second subset 26 of the cells are sealed at the second end face 20. Either of the end faces 18, 20 may be utilized as the inlet face of the resulting filter 10. In a typical cell structure, each inlet cell channel may be bordered on one or more sides by outlet cell channels and vice versa. Each cell channel 22 may have a square cross section or may have other cell geometry, e.g., circular, rectangular, triangular, hexagonal, octagonal, etc. Diesel particular filters are typically made of ceramic materials, such as cordierite, aluminum titinate, mullite, or silicon carbide, and generally include total porosities of between about 40% and 70%.
In operation, contaminated fluid is brought under pressure to an inlet face (either of the end faces 18, 20) and enters the filter 10 via cell channels 22 which have an open end at the given inlet face. Because these cell channels 22, in a typical configuration, may be sealed at the opposite end face, i.e., the outlet face of the body, the contaminated fluid is forced through thin porous walls 14 into adjoining cell channels 22 which are sealed at the inlet face and open at the outlet face. The solid particulate contaminate in the fluid, which is too large to pass through the porous openings in the walls 14, is left behind and a cleansed fluid exits the filter 10 through the outlet cell channels 22.
For the mass production of such filters and substrates, it is highly desirable to be able to rapidly and accurately provide honeycomb structures having desirable end surfaces through a robust and repeatable process. In particular, it is desired to achieve this on filters and substrates having high aspect ratios.